The present invention relates to a pyrotechnic device and more particularly relates to a pyrotechnic device intended to provide a theatrical effect.
It has been proposed before to provide pyrotechnic devices which give a theatrical effect. For example, reference may be made to British Patent 1580579 which discloses a pyrotechnic device which is in wide use at the present point in time to provide a flash or smoke burst effect. This device comprises a receptacle, moulded from plastics material, which is of hollow cylindrical form, having one closed end and one open end. Two pins pass through the closed end, and, on the interior of the receptacle, a fuse wire is connected between the exposed ends of the pins. The receptacle is partly filled with an appropriate pyrotechnic material, and is closed by a closure in the form of a sheet of paper adhered to the open mouth of the receptacle.
The described pyrotechnic device may be inserted in an appropriate socket in a firing box, the socket establishing electric contact with the two pins. An electric current may thus be caused to flow through the fuse wire, which initiates the device. The fuse wire ignites the pyrotechnic material, and the paper sheet is ruptured, since the paper sheet is formed of a material which is weaker than the rest of the receptacle.
Various difficulties exist with this prior device. Firstly, the paper closure is not very strong and is easily broken, especially when a plurality of the devices are packed in a single container, since the pins projecting from the base of one receptacle can easily puncture the paper closure on another receptacle. Furthermore, the adhesive that is used to secure the paper closure to the receptacle is fragile, and will break or snap if the device is dropped. This means that, in either case, pyrotechnic material may become dispersed, or become lodged in the packaging which represents a significant fire hazard.
The device often has to be inserted in the socket under relatively difficult conditions on stage. It is not unknown for stage-hands to panic and then inadvertently pus their fingers through the paper, thus releasing the pyrotechnic material. Also, it is difficult to locate the two pins in alignment with the corresponding pair of holes in the socket--this can lead to fumbling. If the pins catch the socket in an awkward way a spark can be developed, which is clearly undesirable where there is pyrotechnic material around.
Since the closure is only formed of paper, it is possible for moisture to enter the receptacle. This is clearly undesirable, since the presence of moisture may interfere with the operation of the pyrotechnic material. This can be particularly dangerous since when an electric current is passed through the fuse, the pyrotechnic material may not be ignited as intended. The device may, however, ignite as it is being removed from the firing box. This can be very dangerous.
It has been known for the paper covers to be removed from several such devices, and for the pyrotechnic material of all the devices to be combined in one of the receptacles, which, of course, does not have a cover. This provides a very violent effect, and is very dangerous.
It has also been proposed to provide a further device, known as a maroon, which provides the effect of a loud explosion. Such a device has a charge of pyrotechnic material in a closed plastics material housing of uniform strength. A fuse or initiator in the housing is connected to a trailing lead or flex. In using such a device it has to be located in a special tank, called a "bomb tank", and the trailing lead or flex is connected to appropriate terminals. It is necessary to use the bomb tank since the device actually explodes, dispersing portions of the plastic material housing with considerable force.